Since SiC (silicon carbide) power semiconductors have smaller energy loss during energization, smaller amount of heat generation and higher thermal resistance than those of silicon power semiconductors that are widely used at present, they can handle larger electrical power, and are considered actively now. A silicon power semiconductor device has a thermal resistance limit temperature of about 150° C., whereas use of an SiC power semiconductor device at from 200 to 300° C. is considered, and further thermal resistance is also required for a resin to be used for an SiC power semiconductor, and additives to be used for said resin.
Resins that are used as sealing materials and insulation materials for silicon power semiconductor devices had a problem that deterioration is caused when they are used for a long term at a temperature higher than 200° C., and sealing property and electrical insulating property are decreased.
Various additives have been conventionally used so as to prevent deterioration of resins and to maintain performances for a long term. One of such additives is a hindered amine light stabilizer (HALS) having a 2,2,6,6-tetramethylpiperidine backbone, and for example, an HALS having a structure that is excellent in thermal resistance in the case when processing and molding are conducted in a short process such as melt injection molding, and an HALS that is excellent in long-term weather resistance for use in outdoor exposure have been reported (see, for example, Patent Literature 1).
However, in the case when the above-mentioned HALSs are exposed to a condition at higher than 200° C. for a long term, the HALSs themselves are decomposed and cannot maintain performances as a stabilizer for a long term, which consequently leads to insufficient thermal resistance of resins. Furthermore, as an HALS having a high molecular weight, an HALS having a polysiloxane structure obtained by polymerizing a siloxane monomer having a hindered amine backbone is also known (see, for example, Patent Literature 2). Since conventionally-known HALSs having a siloxane structure generally have high polarity and insufficient compatibility with resins, when they were used for a long term, bleeding occurred easily, and thus they were difficult to be used in some uses.